Vertical Monitoring: a data acquisition application for the BaBar experiment

Online Dataflow (ODF) handles data acquisition and processing from the BaBar detector front end electronics through the delivery of complete events to a farm of UNIX nodes. To understand the system, a monitor application, Vertical Monitoring (VMON), has been developed. VMON multicasts UDP packets with performance information from each CPU of the Dataflow system. This information is currently received by a single client on one UNIX node and archived. A ROOT-based GUI is provided on the UNIX application side to control VMON, display the performance of the ODF system in real time and retrieve archived data. VMON is currently used successfully in BaBar to provide diagnostics in the dataflow system and help with projections of future performance.